Many high-performance wireless receivers in cellular communication systems have a linear receiver front-end that is capable of providing both amplitude and phase information for the received signal to the baseband signal processing unit. For this kind of receiver, an automatic gain control (AGC) unit is often needed to bring the fading signal into the linear operating range of the receiver. The requirement of AGC increases not only the design effort, but also the overall cost and power consumption of the receiver.
Hard (amplitude) limiting receivers are known to be small in size, low in cost, and energy efficient. For such receivers, no AGC is required since the dynamic range of the signal amplitude is limited in the front-end. Consequently, hardware cost, and power consumption can be significantly reduced compared to the linear receivers. Hard-limiting receiver front ends are particularly suitable for applications of wireless technology, such as distributed sensor networks, Bluetooth, and Ultra-Wideband (UWB) systems, where lightweight, low cost, and low power consumption are extremely important for the wireless nodes. However, because hard-limiting receivers can provide only reliable phase information for the received signal to the baseband signal processor, hard-limiting receivers are often significantly outperformed by linear receivers. One of the main factors for their inferior performance is the lack of an accurate channel estimate, which is difficult to derive from only the phase information in the received signal.